Meta was essentially shorthand for Metastabilty, which is the stage after rampancy when a AI is a stable state. Sigma(who was Maine's AI) wanted to capture all the AI, and create a Metastable AI, like the Alpha(Church), because at this point, the AI is considered human. Note, if Red vs Blue is ever stated to be canon in the Halo Universe(something it is rapidly approaching). The techniques to create Beta(who is Tex, who is a memory of someone very close the Director, and was a byproduct of flash cloning the Director's mind to create Alpha), could also be used to bring back Cortana. If The Master Chief's mind was flash cloned(perhaps in an effort to create the perfect soldier).

He's referring to a different meta entirely, hence the irony of the joke.

That said, I'm not beyond a tad of literal humour and frankly the info-dump is much appreciated. Although Cortana is probably not dead, given that all the Promethean tech is geared around A.I. in some form or another and clear hints are given towards Cortana wanting to be human (The out of place conversation about the sun.) and then there's the whole constructor being built (though never perfected) to turn A.I. into organic matter.

Let's hope these are not a Chekov's Gun technique...

Also, I'm out of relevant images, so here is a baby that catches fire... make of it what you will.

Anytime, anyway, I was think if the story went something similar to: In an effort to create a perfect AI capable of defending humanity, the Master Chief's mind was flashcloned, however, the trauma he went through due to losing Cortana was enough to create a byproduct, a memory of her. The same way that The Director lost the original Texas(Allison) was enough to create a memory of her.

I would personally prefer your theory, however the only evidence to support it is the vague assumption that 343i would use the hype of Red vs Blue in order to subtly cash-in on the themes already well-explored in their long-running series in order to create a story that was both coherent and rewarded people for being a part of the greater Halo community.

Given 343i's track record with RT it isn't outside the realms of possibilities but it seems a nice long-shot none the less.

I'm so pissed that guy turned out to be Captain Flowers and not Caboose before some kind of catastrophic brain-damage caused by A.I. or something, thus explaining his titanic strength and compatibility with other A.I.

Personally I never really liked the Caboose theory for a few reasons, but partially because the fans seemed to be reaching too much for it. Caboose still had his badass CGI moment, and a nice character got more backstory.